MINOR: h1: add a message flag to indicate that a message carries a response

This flag is H1_MF_RESP. It will be used by the parser during restarts when
it supports requests.
diff --git a/include/proto/h1.h b/include/proto/h1.h
index 365d069..b6c6135 100644
--- a/include/proto/h1.h
+++ b/include/proto/h1.h
@@ -306,7 +306,7 @@
 	h1m->state = H1_MSG_RQBEFORE;
 	h1m->next = 0;
 	h1m->status = 0;
-	h1m->flags = 0;
+	h1m->flags = H1_MF_NONE;
 	h1m->curr_len = 0;
 	h1m->body_len = 0;
 	h1m->err_pos = 0;
@@ -320,7 +320,7 @@
 	h1m->state = H1_MSG_RPBEFORE;
 	h1m->next = 0;
 	h1m->status = 0;
-	h1m->flags = 0;
+	h1m->flags = H1_MF_RESP;
 	h1m->curr_len = 0;
 	h1m->body_len = 0;
 	h1m->err_pos = 0;